This invention relates to an image sensing apparatus such as a combination camera-VTR (camcorder) equipped with an interface for outputting a signal to external equipment, or to a signal processing apparatus which includes such an apparatus.
In a camcorder, which is one example of an image sensing apparatus in the prior art, it is necessary to avoid wear of the recording tape due to contact with a recording head in a situation where the recording head is standing by tracing the same path on the recording tape, as when the camcorder is in the recording standby mode. Further, there is need to minimize consumption of the battery employed as the power supply. For these reasons, the system architecture of such an apparatus is designed to realize conservation of power and prevention of tape wear.
FIG. 23 is a block diagram illustrating the principal components of a system for controlling a camcorder according to the prior art.
As shown in FIG. 23, the system includes a recording start key 1 provided so that the operator may select the start of recording; a camera controller 2 for capturing image information by controlling a lens unit (not shown); a signal processor 3 for encoding the image information, which has been received from the camera controller 2, as digital image data; a recorder controller 4 for controlling a drum motor 5, capstan motor 6 and recording head 7 to record the digital image data, which has been obtained by the encoding processing of signal processor 3, on magnetic recording tape (not shown) serving as a recording medium; and a digital interface 8 for outputting the digital image data, which has been obtained by the encoding processing of signal processor 3, to an external device. The digital interface 8 has a connection terminal 8a. 
The system further includes a power supply unit 9 for supplying peripheral blocks with electric power, and a system controller 10 for controlling the camera controller 2 in conformity with operating-mode selection information obtained from the recording start key 1, which is part of an input unit, the signal processor 3, the recorder controller 4, the digital interface 8 and the power supply unit 9.
FIG. 24 is a flowchart illustrating the operation of the system controller 10 in a case where transition to a recording standby mode has been selected in response to the operator pressing a key. The control operation of the system controller 10 in the recording standby mode will be described with reference to FIG. 24. The recording standby mode refers to a mode in which the camera controller 2 and signal processor 3 are in a state identical with that which prevailed in the recording mode, while the recorder controller 4 places only the drum motor 5 in a state the same as that which prevailed in the recording mode (i.e., controls the drum motor 5 so that it rotates at the same rpm as that in the recording mode) and places the capstan motor 6 and recording head 7 in the OFF state.
When the transition to the recording standby mode is selected in response to the operator pressing a key, the system controller 10 enables a timer interrupt at step S01 in order to measure recording standby time.
The timer interrupt results in the generation of an interrupt at any set time period. A shutdown timer is incremented at step S31, which is within the interrupt, as shown in FIG. 25.
Next, the system controller 10 monitors the recording start key at step S02 and, if an input from this key is sensed at step S03, shifts the mode from the recording standby mode to the recording mode at step S24. By controlling the recorder controller in the recording mode, the capstan roller is driven into rotation and photographic image data is recorded on the magnetic recording tape via the recording head.
The timer interrupt is disabled and the shutdown timer is cleared at step S06. If a key input is not sensed at step S03, the shutdown timer is monitored at step S04. If it is determined that the value measured by the shutdown timer is less than 5 minutes, control returns to step S02. On the other hand, if it is determined that the recording standby mode has continued for five minutes or more, a transition from the recording standby mode to a power shutdown mode is made at step S05. By controlling the power supply unit 9 in the power shutdown mode, the supply of power to the camera controller 2, signal processor 3, recorder controller 4 and digital interface 8 is turned off. Next, at step S06, the timer interrupt is disabled and the shutdown timer is cleared. This series of processing steps completes the operation for conserving power and preventing tape wear.
Many camcorders are equipped with a serial bus in compliance with IEEE 1394-1995 as a digital interface for outputting digital image data to an external device. (This IEEE standard shall be referred to simply as “IEEE 1394” below.) A cable in compliance with IEEE 1394 is composed of two twisted-pair signal lines (to which it is possible to add a power-supply line). In order that the devices in a communications system can recognize one another, a unique ID is set for each device. Furthermore, in order for communication to be controlled over a network, ID information referred to as a node ID (physical address) is set for each device.
If the bus constructing the network undergoes a bus reset, the node IDs are set again. That is, a processing operation for automatically recognizing the make-up of a network becomes necessary when power is introduced or in response to detection of addition/deletion of a network device or of a reset command from an individual device. The ID of each device is set again in such case. Reconfiguration of the network is carried out by this resetting of the network device IDs.
Thus, the digital interface 8, which is a structural component in the prior-art arrangement described above, is in compliance with IEEE 1394. Assume that the digital interface 8 has been connected to an external device. If, under these conditions, the camcorder is forcibly shut down while in the recording standby state, a problem which arises is that in interface networking, a bus reset is generated in order to reconfigure the network and, as a result, processing for interfacing all devices present on the network is suspended.